Rheostat



Alg- 2, 1932 i H. L. BRADLEY -1,869,533

RHEOSTAT Filed June 13, 1928 Figi.

Patented Aug. 2, 1932 HARRY L. BRADLEY,

MENTS, TO ALLEN-BRADLEY COMPANY,

TION OF WISCONSIN or MILWAUKEE, WISCONSIN, AssIGNon, EY ivIEsNs AssIGN;

on MILWAUKEE, WISCONSIN,l A eonPonA-- Application led June 13,

ber which is coated with a viscous material,

to retain the member in any position of adjustment.

Another object of this invention. resides in the provision of a resistor of the character described which is so constructed that after assembling of the threaded adjusting member with the body or housing, detachment of the adjusting member is prevented.

And a still further object of this invention resides in the provision of a resistor of the character described which has the number of its parts reduced to a minimum without impairing its eii'iciency. Y

With the above and other objects in view, which will appear as the descriptionl proceeds, my invention resides in the novelconstruction, combination and arrangement `of parts substantially as hereinafter described and more particularly defmedby the appended claims, -it being `understood that such changes in the precise embodiment of the hereindisclosed invention may be madeas come Within the scope of the claims.

1n the accompanying drawing, I have illustrated one complete example of thephysical embodiment of my invention constructed according to the best mode I have so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a transverse, sectional view, taken through a resistor embodying my invention, parts thereof being in elevation;

Figure 2 is a cross sectional view, taken through Figure 1 on the plane of the line 2-.-2; and

Figure 3 is an enlarged detail, fragmentary view of a portion of the adjusting member thread illustrating the viscous material with which it is coated.

60 Referring now more particularly to the acthe bushing flange.

1928. Serial No. 284,997.

companying drawing, in which like numerals designate like parts throughout the several views, V5 represents a mounting means having an aperture 6 l1n which a iianged bushing member 7 is positioned, being held by a clamping nut A8 threaded on the outer end of the bushing member. I v

A threaded aperture 9 extends throughout the major portion of the bushing 7 to receive an adjusting screw 10 provided with an actuating member 11,the inner end 12 of the screw being arranged to compress the discs 13 of a resistance unit suitably mounted at the inner end of the bushing member, as hereafter de. scribed.

The inner end of th-e bushing member has a counterbore 14: which communicates with the threaded bore 9 and a second counterbore 15 of a diameter slightly less than that of the bushing iange to form a relatively thin annular wall 16 extending from the inner end of The adjusting screw 10 is annularly recessed adjacent its end12, as at 17, to receive a split resilient ring 18. The ring 18 may be positioned on the screw prior to assembling bushing member 7, and expands to its position illustrated in Figure 1, when the adjusting screw is threaded into its aperture a suiiicient distance to align the ring with the counterbore 14, to prevent detachment of the adjusting screw. The resistor discs 13 are positioned in the bore 19 of a tubular shell or housing member 20 formed of. suitable insulating material and having its outer end closed by an apertured wall 21, a rivet or other securing means 22 having its head positioned within thev bore 19 passing through the aperture to secure a terminal member 23 in the adjacent resistor disc. An annular flange 24y of a diameter to snugly fit within the counterbore 15 is formed on the opposite end of the member 20 and has its outer corner beveled, as at 25, over which the edge of the annular wall16 is spun or pressed to assemble the member 20 with the bushing member; Y

A second terminal 26 having an annular ring 27, the outer diameter of which'is subthe adjusting member with thev electrical contact with panel or other suitable stantially equal to the diameter of the flange 24 and the inner diameter of which is substantially equal to the diameter of the counterbore 14, is impinged between the adjacent ends of the member 2O and the bushing` member, the terminal proper extending through an opening 28 in the flange 16.

A disc 29 formed of suitable metal, preferably brass, receives the pressure. imposed by the adjusting screw and imparts it. to theserie's of discs 13 forming the resistor unit tov vary its resistance to electric currents. Y

Heretofore it has been found that where devices of some time the thread of the adjusting screw becomes loose in its bushing, due primarily to the excessive wear incident to the metal upon metal contact. This condition was especially objectionable in small-er resistors and when the pressure of the adjusting screw was at a minimum, often requiring but the mere touch oi a hand to change its settingand thus disturb possibly a critical resistance value and to preclude this possibility thek screw 10 -is coated with a suitable viscous sub; stance 30 such as a composition of asphalt, benzol'and oil which retains its viscosity indefinitely and at all times tends to `restrain movement of the adjusting screw 'and .prevent the wear on the parts.

From the foregoing description, taken in connection with the accompanying drawing, it will be readily apparent to those skilled in the art to which an invention of the character described appertains, that I provide ya resistor of the character described which is extremely compact, has a minimum number of parts and in which the setting is not easily disturbed.

What I claim asmy invention is:

1. A compression rh-eostat, comp-rising a centrally bored bushing member having a counterbore at one end to form a shoulder inwardly of'said end, the `annular wall of said counterbore having an opening adjacent the shoulder, a terminal having a part within the counterbore in engagement with said shoulder and a portion extending through said opening, a tubular housing member havmg lone end vopen and received within the` counterbore to engage the terminal part therein whereby said terminal member part is disposedbetween the shoulder and said end of the hoesin member, means securing the housing memer within the counterbore, a compressible resistance element positioned within the housing member,'and screw means threaded in the bushing member central bore for adjusting the pressure on the resistance element.

2. A compression rheostat of the character described, comprising a shell of insulating material having one end open, a compressible resistance element within the shell, a terminal member for the element,-a tubular bushthis nature have-beenin use for ing member counterbored at one end to receive part of the terminal member and the open end portion of the shell, means securing said open end portion of the shell in the bushing member counterbore with the terminal member part clamped between the shell and the bottom ofthe counterbore, and an adjusting screw threaded in the bushing member for. applying pressure on said resistance element. i

3. A compression rheostat of the character described, comprising a shell of insulating material having one end open, a compressible resistance element `within the shell, a terminal member carried by the closed end of the shell and electrically connected with one end of the element, `a second terminal member, a counterbored bushing member, a flange on the open end of the shell adapted to be received in the bushingrmember counterbore with a portion of the second terminal member between the bottom of the kbushing member counterbore and the shell, an abutment carried by the bushing member and engaged over the shell-carried flange to secure the parts assembled with the second terminal member in electrical connection with the bushing member, and an adjusting screw threaded in the bushing member for applying pressure to the resistance element. 9 4 A compression rheostat of the character described, comprising a shell of insulating material, a compressible resistance 'element within the shell, a terminal member carried at one end of the shell and electrically conl* nected with one end of the resistance element, a flange von the opposite end of the shell, a bushing member having a counterbore adapted to receive the flanged end of the shell, a second terminal member having a portion substantially the same diameter 'as the flange and provided with an aperture of greater diameter than the resistance element, an abutment carried by the edge of the bushing counterbore andspun over the shell `carried flange to secure the `parts together with the apertured portion of the vsecond terminal member disposed therebetween, and an adjusting screw threaded in the bushing member for applying pressure on the resistance m element, the aperture inthe said second mentioned terminal member permitting the ladj usting screw to extend therethrough.

compression rhe'ostat, comprising a tubular bushing having Vportions of different internal `diameters to provide a plurality of shoulders, la tubular shell of insulating material having 'one endfopen and received in the portion of greatest internal diameter, a compressible resistance element within the shell, a terminal for one end of the resistance element having a part received vin said bushing portion of greatest internal diameter between the shoulder at its innerend and said end ofthe shell, an-adjustingscrew threaded on the bushing portion of the smallest internal diameter with its inner end portion received in a bushing portion of intermediate diameter and adapted to engage the adjacent end of the resistance element, and means within the bushing member portion of intermediate internal diameter engaging the adjusting screw and the shoulder at the inner end of the portion of intermediate internal diameter for preventing detachment of the screw from the bushing.

6. A compression rheostat, comprising a tubular bushing having a double counterbore at one end the bottoms of which form spaced shoulders, a tubular shell of insulating material having one end open and secured in the outermost counterbore, a compressible resistance element in the shell, a terminal for one end of the resistance element, and having a part received in said outer counterbore between the bottom of said counterbore and the adjacent end of the shell and having a part projecting through an opening in the annular wall of the outer counterbore, an adjusting screw threaded in the bushing and having its inner end portion received in the inner counterbore and passing through an opening in the terminal member to engage the adjacent end of the compressible resistance element, and means within the inner counterbore carried by the adjusting screw and engageable with the bottom of said inner counterbore for preventing detachment of the screw Jrom the bushing. In testimonj7 whereof I affixed my signature.

HARRY L. BRADLEY.

have hereunto 

